Complex fragment emission in the 200-MeV 4He+natAg,197Au reactions

Spectra, angular distributions, and cross sections have been measured for Z=3 endash 14 fragments produced in 200-MeV 4 He-induced reactions on nat Ag and 197Au targets. In addition, isotopic yields were measured at forward angles. Two-component moving-source fits have been performed on the data to evaluate the relative contributions of nonequilibrium and equilibrium emission mechanisms. At forward angles, the complex fragment yields are dominated by nonequilibrium emission, with IMF energies extending from the emission barrier to momenta in excess of the incident beam. Backward of 90 degree the yields are nearly isotropic and exhibit spectra consistent with emission from an equilibrated composite nucleus. copyright 1997 The American Physical Society